For sickle hemoglobin, a theoretical formalism has been written which appears to be capable of explaining the role of non-HbS proteins in the gelation of HbS in mixed solutions. The capabilities of this approach are being studied in mixtures of HbS with HbS, HbF and HbCH. Gelation kinetics, equilibrium solubility, and incorporation into the gel are being looked at. With nucleic acids, a stopped-flow method for studying H-exchange of polynucleotides is being systematically developed. The method is applicable to nucleic acids even when they are complexed to major anounts of proteins, and studies on RNA in ribosomes and on DNA in chromatin are to be pursued. The method can measure amount of helical structure, H-bonding of nucleic acid to the protein, stability of structure, and changes in structure, as well as the interesting "4th dimension" of structure, the opening-closing or breathing behavior of polynucleotides.